On v5.8 when doing seccomp syscall rewrites (e.g. getpid into getppid
as seen in the seccomp selftests), trace (and audit) correctly see the
rewritten syscall on entry and exit:
seccomp_bpf-1307 [000] .... 22974.874393: sys_enter: NR 110 (...
seccomp_bpf-1307 [000] .N.. 22974.874401: sys_exit: NR 110 = 1304
With mainline we see a mismatched enter and exit (the original syscall
is incorrectly visible on entry):
seccomp_bpf-1030 [000] .... 21.806766: sys_enter: NR 39 (...
seccomp_bpf-1030 [000] .... 21.806767: sys_exit: NR 110 = 1027
When ptrace or seccomp change the syscall, this needs to be visible to
trace and audit at that time as well. Update the syscall earlier so they
see the correct value.
Reported-by: Michael Ellerman <[email protected]>
Fixes: d88d59b64ca3 ("core/entry: Respect syscall number rewrites")
Cc: Thomas Gleixner <[email protected]>
Cc: Kyle Huey <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
---
kernel/entry/common.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index 18683598edbc..6fdb6105e6d6 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -60,13 +60,15 @@ static long syscall_trace_enter(struct pt_regs *regs, long
syscall,
return ret;
}
+ /* Either of the above might have changed the syscall number */
+ syscall = syscall_get_nr(current, regs);
+
if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
trace_sys_enter(regs, syscall);
syscall_enter_audit(regs, syscall);
- /* The above might have changed the syscall number */
- return ret ? : syscall_get_nr(current, regs);
+ return ret ? : syscall;
}
static __always_inline long
--
2.25.1
